Family living among birds

Abstract

Family cohesion in birds is often explained as a product of limitations on breeding opportunities leading to delayed dispersal among the offspring. Yet, it is not independent reproduction but floating (queuing outside the natal territory for a breeding opportunity) that is the alternative to delaying dispersal. In contrast to a strong phylogenetic bias in cooperative breeding that has been taken to indicate a hard‐wired behaviour maintained by evolutionary inertia, offspring behaviour is plastic and facultative in group living in the short term, indicating that family cohesion is under selection. Non‐breeding offspring could gain inclusive fitness that would promote family cohesion from delaying dispersal and providing alloparental care to subsequent broods to boost group productivity. This holds in particular for offspring hatched from early broods in multi‐brooded species that have the opportunity to gain inclusive fitness from help in rearing siblings hatched from later broods in the same season. Yet, seasonality will circumscribe the potential for alloparenting to be the immediate factor selecting for family cohesion. The option of gaining inclusive fitness from providing alloparental care is not open to the offspring among single‐brooded species until after they have survived a non‐breeding season, rather indicating kin cooperation returning enhanced survival prospects from general group living effects as a more immediate factor selecting for family cohesion. Indeed, a variety of family groups maintained in the absence of alloparental care underlines the capacity of general group living enhancing survival as a primary agent selecting for family cohesion. These seasonal constraints on fitness components selecting for family cohesion may contribute to the large scale geographical pattern with a relative paucity of family cohesions among bird species in the northern hemisphere.

Collectivism–Individualism, Family Ties, and Philopatry

“…At a minimum, our conjecture is supported by the fact that cooperative breeding in birds and eusocial systems in insects are more common, or in the case of eusociality, more eusocial, in tropical regions for many different taxa (e.g., birds (Brown 1987;Ekman 2006 ;Blumstein and Møller 2008 ), wasps (Wilson 1971 )). The incidence of cooperative breeding in birds has been shown to correlate positively with temporal variation in certain climatic factors, especially rainfall (Jetz and Rubenstein 2011 ).…”

Cryptic Kin Selection: Kin Structure in Vertebrate Populations and Opportunities for Kin‐Directed Cooperation

“…Indeed, such benefits of nepotistic sharing of resources result in delayed dispersal even in the absence of cooperative breeding (Ekman et al. 2004; Ekman 2006).…”

The cost of being alone: the fate of floaters in a population of cooperatively breeding pied babblers Turdoides bicolor

“…Cooperative breeding behaviour, where non‐reproductive adults help to raise the young of others is often assumed to occur as a result of the benefits of group‐living and the constraints on successful dispersal and independent breeding (Emlen 1982, Koenig et al 1992). Groups are often formed by the retention of young on the natal territory beyond the age of sexual maturity and much debate has centred around why individuals in cooperative societies delay breeding and remain at home (reviewed in Koenig et al 1992, Ekman 2006). While it is acknowledged that individuals may gain indirect fitness benefits by helping to raise kin (Hamilton 1964, Koenig et al 1992), the occurrence of species that remain on the natal territory without helping suggests that direct benefits are sufficient for the occurrence of delayed dispersal and group formation (Alexander 1974, Kokko and Ekman 2002).…”